Effects of systemic inflammation on the network oscillation in the anterior cingulate cortex and cognitive behavior.

Network oscillation in the anterior cingulate cortex (ACC) plays a key role in attention, novelty detection and anxiety; however, its involvement in cognitive impairment caused by acute systemic inflammation is unclear. To investigate the acute effects of systemic inflammation on ACC network oscillation and cognitive function, we analyzed cytokine level and cognitive performance as well as network oscillation in the mouse ACC Cg1 region, within 4 hours after lipopolysaccharide (LPS, 30 µg/kg) administration. While the interleukin-6 concentration in the serum was evidently higher in LPS-treated mice, the increases in the cerebral cortex interleukin-6 did not reach statistical significance. The power of kainic acid (KA)-induced network oscillation in the ACC Cg1 region slice preparation increased in LPS-treated mice. Notably, histamine, which was added in vitro, increased the oscillation power in the brain slices from LPS-untreated mice; for the LPS-treated mice, however, the effect of histamine was suppressive. In the open field test, frequency of entries into the center area showed a negative correlation with the power of network oscillation (0.3 µM of KA, theta band (3-8 Hz); 3.0 µM of KA, high-gamma band (50-80 Hz)). These results suggest that LPS-induced systemic inflammation results in increased network oscillation and a drastic change in histamine sensitivity in the ACC, accompanied by the robust production of systemic pro-inflammatory cytokines in the periphery, and that these alterations in the network oscillation and animal behavior as an acute phase reaction relate with each other. We suggest that our experimental setting has a distinct advantage in obtaining mechanistic insights into inflammatory cognitive impairment through comprehensive analyses of hormonal molecules and neuronal functions.

Interactions between Age-Related Type 2 Diabetes and the Small Intestine.

The number of patients with type 2 diabetes is increasing worldwide. The mechanisms leading to type 2 diabetes and its complications is being researched; however, the pathological mechanisms of diabetes in the small intestine remain unclear. Therefore, we examined these pathological mechanisms in the small intestine using a mouse model of type 2 diabetes (KK-Ay/TaJcl) aged 10 and 50 weeks. The results showed that diabetes worsened with age in the mice with type 2 diabetes. In these mice, advanced glycation end products (AGEs) in the small intestine and mast cell expression increased, whereas diamine oxidase (DAO) decreased; increased tumor necrosis factor (TNF)-α and histamine levels in the plasma and small intestine were also detected. Additionally, the expression of zonula occludens (ZO)-1 and Claudin1 and cell adhesion molecules in the small intestine reduced. These results exacerbated with age. These findings indicate that type 2 diabetes causes AGE/mast cell/histamine and TNF-α signal transmission in the small intestine and decreases small intestinal wall cell adhesion molecules cause TNF-α and histamine to flow into the body, worsening the diabetic condition. In addition, this sequence of events is suggested to be strengthened in aged mice with type 2 diabetes, thus exacerbating the disease. These findings of this study may facilitate the elucidation of the pathological mechanisms of type 2 diabetes and its associated complications.

Brain histamine improves colonic hyperpermeability through the basal forebrain cholinergic neurons, adenosine A2B receptors and vagus nerve in rats.

Intestinal barrier dysfunction, leaky gut, is implicated in various diseases, including irritable bowel syndrome (IBS) and neurodegenerative conditions like Alzheimer's disease. Our recent investigation revealed that basal forebrain cholinergic neurons (BFCNs), critical for cognitive function, receive signals from butyrate and orexin, playing a role in regulating intestinal barrier function through adenosine A2B signaling and the vagus. This study explores the involvement and function of brain histamine, linked to BFCNs, in the regulation of intestinal barrier function. Colonic permeability, assessed by quantifying absorbed Evans blue in rat colonic tissue, showed that histamine did not affect increased colonic permeability induced by LPS when administered subcutaneously. However, intracisternal histamine administration improved colonic hyperpermeability. Elevating endogenous histamine levels in the brain with SKF91488, a histamine N-methyltransferase inhibitor, also improved colonic hyperpermeability. This effect was abolished by intracisternal chlorpheniramine, an histamine H1 receptor antagonist, not ranitidine, an H2 receptor antagonist. The SKF91488-induced improvement in colonic hyperpermeability was blocked by vagotomy, intracisternal pirenzepine (suppressing BFCNs activity), or alloxazine (an adenosine A2B receptor antagonist). Additionally, intracisternal chlorpheniramine injection eliminated butyrate-induced improvement in colonic hyperpermeability. These findings suggest that brain histamine, acting via the histamine H1 receptor, regulates intestinal barrier function involving BFCNs, adenosine A2B signaling, and the vagus. Brain histamine appears to centrally regulate intestinal barrier function influenced by butyrate, differentiating its actions from peripheral histamine in conditions like IBS, where mast cell-derived histamine induces leaky gut. Brain histamine emerges as a potential pharmacological target for diseases associated with leaky gut, such as dementia and IBS.

Histamine H1 Receptor-Mediated JNK Phosphorylation Is Regulated by Gq Protein-Dependent but Arrestin-Independent Pathways.

Arrestins are known to be involved not only in the desensitization and internalization of G protein-coupled receptors but also in the G protein-independent activation of mitogen-activated protein (MAP) kinases, such as extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), to regulate cell proliferation and inflammation. Our previous study revealed that the histamine H1 receptor-mediated activation of ERK is dually regulated by Gq proteins and arrestins. In this study, we investigated the roles of Gq proteins and arrestins in the H1 receptor-mediated activation of JNK in Chinese hamster ovary (CHO) cells expressing wild-type (WT) human H1 receptors, the Gq protein-biased mutant S487TR, and the arrestin-biased mutant S487A. In these mutants, the Ser487 residue in the C-terminus region of the WT was truncated (S487TR) or mutated to alanine (S487A). Histamine significantly stimulated JNK phosphorylation in CHO cells expressing WT and S487TR but not S487A. Histamine-induced JNK phosphorylation in CHO cells expressing WT and S487TR was suppressed by inhibitors against H1 receptors (ketotifen and diphenhydramine), Gq proteins (YM-254890), and protein kinase C (PKC) (GF109203X) as well as an intracellular Ca2+ chelator (BAPTA-AM) but not by inhibitors against G protein-coupled receptor kinases (GRK2/3) (cmpd101), ß-arrestin2 (ß-arrestin2 siRNA), and clathrin (hypertonic sucrose). These results suggest that the H1 receptor-mediated phosphorylation of JNK is regulated by Gq-protein/Ca2+/PKC-dependent but GRK/arrestin/clathrin-independent pathways.

H2 antihistamines: May be useful for combination therapies in cancer?

Cancer morbimortality is still a great concern despite advances in research and therapies. Histamine and its receptors' ligands can modulate different biological responses according to the cell type and the receptor subtype involved. Besides the wide variety of histamine functions in normal tissues, diverse roles in the acquisition of hallmarks of cancer such as sustained proliferative signaling, resistance to cell death, angiogenesis, metastasis, altered immunity and modified microenvironment have been described. This review summarizes the present knowledge of the various roles of histamine H2 receptor (H2R) ligands in neoplasias. A bioinformatic analysis of human tumors showed dissimilar results in the expression of the H2R gene according to tumor type when comparing malignant versus normal tissues. As well, the relationship between patients' survival parameters and H2R gene expression levels also varied, signaling important divergences in the role of H2R in neoplastic progression in different cancer types. Revised experimental evidence showed multiple effects of H2R antihistamines on several of the cited hallmarks of cancer. Interventional and retrospective clinical studies evaluated different H2R antihistamines in cancer patients with two main adjuvant uses: improving antitumor efficacy (which includes regulation of immune response) and preventing toxic adverse effects produced by chemo or radiotherapy. While there is a long path to go, research on H2R antihistamines may provide new opportunities for developing more refined combination therapeutic strategies for certain cancer types to improve patients' survival and health-related quality of life.

Intrinsic endothelial hyperresponsiveness to inflammatory mediators drives acute episodes in models of Clarkson disease.

Clarkson disease, or monoclonal gammopathy-associated idiopathic systemic capillary leak syndrome (ISCLS), is a rare, relapsing-remitting disorder featuring the abrupt extravasation of fluids and proteins into peripheral tissues, which in turn leads to hypotensive shock, severe hemoconcentration, and hypoalbuminemia. The specific leakage factor(s) and pathways in ISCLS are unknown, and there is no effective treatment for acute flares. Here, we characterize an autonomous vascular endothelial defect in ISCLS that was recapitulated in patient-derived endothelial cells (ECs) in culture and in a mouse model of disease. ISCLS-derived ECs were functionally hyperresponsive to permeability-inducing factors like VEGF and histamine, in part due to increased endothelial nitric oxide synthase (eNOS) activity. eNOS blockade by administration of N(γ)-nitro-l-arginine methyl ester (l-NAME) ameliorated vascular leakage in an SJL/J mouse model of ISCLS induced by histamine or VEGF challenge. eNOS mislocalization and decreased protein phosphatase 2A (PP2A) expression may contribute to eNOS hyperactivation in ISCLS-derived ECs. Our findings provide mechanistic insights into microvascular barrier dysfunction in ISCLS and highlight a potential therapeutic approach.

Identification and characterization of an endogenous biomarker of the renal vectorial transport (OCT2-MATE1).

The renal tubular organic cation transporter 2 (OCT2) and multidrug and toxin extrusion protein 1 (MATE1) mediate the vectorial elimination of many drugs and toxins from the kidney, and endogenous biomarkers for vectorial transport (OCT2-MATE1) would allow more accurate drug dosing and help to characterize drug-drug interactions and toxicity. Human serum uptake in OCT2-overexpressing cells and metabolomics analysis were carried out. Potential biomarkers were verified in vitro and in vivo. The specificity of biomarkers was validated in renal transporter overexpressing cells and the sensitivity was investigated by Km . The results showed that the uptake of thiamine, histamine, and 5-hydroxytryptamine was significantly increased in OCT2-overexpressing cells. In vitro assays confirmed that thiamine, histamine, and 5-hydroxytryptamine were substrates of both OCT2 and MATE1. In vivo measurements indicated that the serum thiamine level was increased significantly in the presence of the rOCT2 inhibitor cimetidine, and the level in renal tissue was increased significantly by the rMATE1 inhibitor pyrimethamine. There were no significant changes in the uptake or efflux of thiamine in cell lines overexpressed OAT1, OAT2, OAT3, MRP4, organic anion transporting polypeptide 4C1, P-gp, peptide transporter 2, urate transporter 1, and OAT4. The Km for thiamine with OCT2 and MATE1 were 71.2 and 10.8 µM, respectively. In addition, the cumulative excretion of thiamine at 2 and 4 h was strongly correlated with metformin excretion (R2  > 0.6). Thus, thiamine is preferentially secreted by the OCT2 and MATE1 in renal tubules and can provide a reference value for evaluating the function of the renal tubular OCT2-MATE1.

Protective effects of an alcoholic extract of Kaempferia galanga L. rhizome on ethanol-induced gastric ulcer in mice.

ETHNOPHARMACOLOGICAL RELEVANCE: The rhizome of Kaempferia galanga L., a medicinal and edible Plant, was widely distributed in many Asian and African counties. It has been traditionally used to treat gastroenteritis, hypertension, rheumatism and asthma. However, there is a lack of modern pharmacology studies regarding its anti-gastric ulcer activity. AIM OF THE STUDY: The objective of this study is to investigate the protective effects of an extract from K. galanga L. rhizome (Kge) and its active components kaempferol and luteolin on ethanol-induced gastric ulcer. MATERIALS AND METHODS: The kge was prepared by ultrasonic-assisted extraction, and the contents of kaempferol and luteolin were determined by HPLC. The mice were randomly divided into seven groups: blank control (0.5 % CMC-Na; 0.1 mL/10 g), untreatment (0.5 % CMC-Na; 0.1 mL/10 g), Kge (100, 200 and 400 mg/kg), kaempferol (100 mg/kg) and luteolin (100 mg/kg) groups. The mice were treated intragastrically once daily for 7 days. At 1 h post the last administration, the mice in all groups except the blank control group were intragastrically administrated with anhydrous alcohol (0.1 mL/10 g) once to induce gastric ulcer. Then, fasting was continued for 1 h, followed by sample collection for evaluation by enzyme-linked immunosorbent assay and real-time reverse transcription polymerase chain reaction assay. RESULTS: The contents of kaempferol and luteolin in Kge were determined as 3713 µg/g and 2510 µg/g, respectively. Alcohol induced severely damages with edema, inflammatory cell infiltration and bleeding, and the ulcer index was 17.63 %. After pre-treatment with Kge (100, 200 and 400 mg/kg), kaempferol and luteolin, the pathological lesions were obviously alleviated and ulcer indices were reduced to 13.42 %, 11.65 %, 6.54 %, 3.58 % and 3.85 %, respectively. In untreated group, the contents of Ca2+, myeloperoxidase, malondialdehyde, NO, cyclic adenosine monophosphate and histamine were significantly increased, while the contents of hexosamine, superoxide dismutase, glutathione peroxidase, and prostaglandin E2 were significantly decreased; the transcriptional levels of IL-1α, IL-1ß, IL-6, calcitonin gene related peptide, substance P, M3 muscarinic acetylcholine receptor, histamine H2 receptor, cholecystokinin 2 receptor and H+/K+ ATPase were significantly increased when compared with the blank control group. After pre-treatment, all of these changes were alleviated, even returned to normal levels. Kge exhibited anti-gastric ulcer activity and the high dose of Kge (400 mg/kg) exhibited comparable activity to that of kaempferol and luteolin. CONCLUSION: The study showed that K. galanga L., kaempferol, and luteolin have protective effects against ethanol-induced gastric ulcers. This is achieved by regulating the mucosal barrier, oxidative stress, and gastric regulatory mediators, as well as inhibiting the TRPV1 signaling pathway and gastric acid secretion, ultimately reducing the gastric ulcer index.

Leaves and pseudostems extract of Curcuma longa attenuates immunoglobulin E/bovine serum albumin-stimulated bone marrow-derived cultured mast cell activation and passive cutaneous anaphylaxis in BALB/c mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Curcuma longa, known as turmeric, is an herbaceous perennial plant belonging to the genus Curcuma. It is dispersed throughout tropical and subtropical regions worldwide. Since ancient times, turmeric has been used as an ethnomedicinal plant in the Ayurvedic system, particularly in Asian countries. Rhizomes of turmeric possess several pharmacological properties that give high value as a medicinal remedy for treating a range of conditions, including inflammation, pain, allergies, and digestive issues. Moreover, turmeric leaves and pseudostems also contain a variety of health-enhancing secondary metabolites, such as curcumin, flavonoids, and other phenolic compounds, which exhibit anti-inflammatory, antitumor, antibacterial, and antioxidant properties. AIM OF THE STUDY: Allergic diseases are a group of immune-mediated disorders mainly caused by an immunoglobulin E (IgE)-dependent immunological response to an innocuous allergen. Therefore, this study aimed to investigate the effect of leaves and pseudostems extract of turmeric (TLSWE-8510) on IgE/bovine serum albumin (BSA)-stimulated allergic responses in mouse bone marrow-derived cultured mast cells (BMCMCs) and passive cutaneous anaphylaxis (PCA) in BALB/c mice. MATERIALS AND METHODS: The effect of TLSWE-8510 on mast cell degranulation has been evaluated by investigating the release of ß-hexosaminidase and histamine in IgE/BSA-stimulated BMCMCs. Additionally, anti-allergic properties of TLSWE-8510 on IgE/BSA-stimulated BMCMCs were investigated using suppression of nuclear factor-kappa B (NF-κB), and spleen tyrosine kinase (Syk)-linker for T-cell activation (LAT)-extracellular-signal-regulated kinase (ERK)-GRB2 associated binding protein 2 (Gab2) signaling pathway and downregulation of allergy-related cytokines and chemokines expression. Furthermore, in vivo, studies were conducted using IgE-mediated PCA in BALB/c mice. RESULTS: TLSWE-8510 treatment significantly inhibited the degranulation of IgE/BSA-stimulated BMCMCs by inhibiting the release of ß-hexosaminidase and histamine dose-dependently. Additionally, TLSWE-8510 reduced the expression of high-affinity IgE receptors (Fc epsilon receptor I-FcεRI) on the surface of BMCMCs and the binding of IgE to FcεRI. Besides, the expression of cytokines and chemokines is triggered by IgE/BSA stimulation via activating the allergy-related signaling pathways. TLSWE-8510 dose-dependently downregulated the mRNA expression and the production of allergy-related cytokines (interleukin (IL)-1ß, IL-3, IL-4, IL-5, IL-6, IL-13, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ), and chemokines (thymus and activation-regulated chemokine (TARC), and regulated upon activation, normal T cell expressed and secreted (RANTES)) by regulating the phosphorylation of downstream signaling molecules, NF-κB, and Syk, LAT, ERK and Gab2 in IgE/BSA-stimulated BMCMCs. Moreover, PCA reaction in IgE/BSA-stimulated BALB/c mice ears was effectively decreased by TLSWE-8510 treatment in a dose-dependent manner. CONCLUSIONS: These results collectively demonstrated that TLSWE-8510 suppressed mast cell degranulation by inhibiting the release of chemical mediators related to allergies. TLSWE-8510 downregulated the allergy-related cytokines and chemokines expression and phosphorylation of downstream signaling molecules in IgE/BSA-stimulated BMCMCs. Furthermore, in vivo studies with IgE-mediated PCA reaction in the BALB/c mice ears were attenuated by TLSWE-8510 treatment. These findings revealed that TLSWE-8510 has the potential as a therapeutic agent for the treatment of allergic diseases.

VAMP7 knockdown in secretory granules impairs CCL2 secretion in mast cells.

Mast cells (MCs) possess numerous potent inflammatory mediators and undergo differential regulation in response to antigen (Ag) stimulation. Among the regulatory systems governing secretory responses, soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) play a pivotal role in facilitating granule-plasma membrane fusion and subsequent secretion. Our previous investigation documented the involvement of vesicle-associated membrane protein 3 (VAMP3) in regulating cytokine secretions in RBL-2H3 cells, a model for MC IgE-mediated responses. In addition to VAMP3, VAMP7 is expressed in MCs, but its functional role remains elusive. The present study seeks to explore VAMP7-specific regulatory mechanisms in MCs, shedding light on one of the mechanisms governing heterogeneous secretory responses in these cells. Murine bone marrow-derived mast cells (BMMCs) were examined to analyze the subcellular distribution of inflammatory mediators, specifically TNFα, CCL2, and histamine, and VAMPs (i.e., VAMP3, VAMP7, and VAMP8). Immunocytochemistry and the transient expression of fluorescent protein-conjugated target proteins were used to discern the distribution of various inflammatory mediators and VAMP7 through confocal laser scanning microscopy. Each inflammatory mediator (TNFα, CCL2, and histamine) was found in secretory granules of different sizes within BMMCs. VAMP7 exhibited a distinct distribution compared to VAMP3 in these granules. Notably, an overlapping distribution was observed between VAMP7 and CCL2, but not between VAMP7 and TNFα or VAMP7 and histamine. This suggests that CCL2 resides within VAMP7-expressing granules and is subject to VAMP7-dependent secretory regulation. Consistently, BMMCs with VAMP7 knockdown showed markedly reduced CCL2 secretion after Ag stimulation. These observations underscore the heterogeneity of MC secretory responses and unveil a novel VAMP7-dependent CCL2 secretion mechanism within MCs. This discovery might pave the way for the development of more precise therapeutic strategies to modulate MC secretion in allergic conditions.

Targeting Mast Cells: Sodium Cromoglycate as a Possible Treatment of Lipedema.

Background: Mast cells are immune cells that mediate hypersensi-tivity and allergic reactions in the body, secreting histamine and other inflammatory molecules. They have been associated with different inflammatory conditions such as obesity and other adipose tissue di-sorders. Lipedema is a chronic disease characterized by an abnormal accumulation of adipose tissue on the legs and arms, pain, and other symptoms. Mast cells may play a role in the pathology of lipedema. Objective: Pilot study to determine levels of histamine and its metabolites in lipedema subcutaneous adipose tissue (SAT) biopsy samples, and to test sodium cromoglycate for the treatment of mast cells in women with lipedema. Methods: Biopsies from lipedema and control SAT were collected and analyzed histologically for the presence of mast cells. Mass spec-trometry was used to measure the levels of histamine, a key marker of mast cells, and its metabolites in SAT in women with lipedema and controls, and after a group of women with lipedema were administered oral and topical doses of sodium cromoglycate for two weeks. Results: Histological examination of biopsies from lipedema patients confirmed the presence of mast cells. Metabolomic analysis revealed high levels of histamine and its metabolites in samples from women with lipedema compared to controls. Following a two-week treatment period, lipedema tissue samples exhibited reduced levels of histamine, suggesting a reduction of mast cell activity. Conclusion: Sodium cromoglycate has the ability to stabilize mast cells and reduce histamine levels in lipedema patients, which could be useful in lowering the symptoms of lipedema.

The involvement of transient receptor potential channels in mast cell activation by microbubbles.

This study was to explore the activation of mast cells by microbubbles, with the focus on transient receptor potential (TRP) channels mediated degranulation and calcium influx. Bone marrow-derived mast cells (BMMCs) were primarily obtained from femurs in mice and induced differentiation for 4 weeks. After the purity identification, BMMCs were contacted by homogeneous microbubbles with the diameter of 1 mm for 1 h. ß-hexosaminidase and histamine levels in supernatants were assessed by enzyme-linked immunosorbent assay (ELISA) and the CD63 expression was tested by flow cytometry. The intracellular calcium binding with Fluo-4 AM dyes in BMMCs was observed under the fluorescence microscope and the mean fluorescence intensity was quantitatively measured by flow cytometry. ß-hexosaminidase release, histamine concentration, CD63 expression and calcium influx were significantly increased in BMMCs group upon microbubble stimulation compared to the control groups. After preconditioning with the available inhibitors and microbubble contact, only transient receptor potential vanilloid 1 (TRPV1) and TRPV4 inhibitors robustly suppressed the microbubble-induced degranulation. Likewise, the elevated fluorescence intensity of cytosolic calcium level was also significantly weaken. The results demonstrated microbubble stimulus effectively promoted BMMCs degranulation, which could be substantially restrained by inhibitors targeted for blocking TRPV1 or TRPV4 channel. The alternation of intracellular calcium level in BMMCs was consistent with the changes of degranulation capacity. It's suggested that the activation of BMMCs by microbubbles may involve specific TRP calcium dependent channels.

Histamine-producing bacteria and their role in gastrointestinal disorders.

INTRODUCTION: Gut microbiota produces thousands of metabolites, which have a huge impact on the host health. Specific microbial strains are able to synthesize histamine, a molecule with a crucial role in many physiologic and pathologic mechanisms of the host. This function is mediated by the histidine decarboxylase enzyme (HDC) that converts the amino acid histidine to histamine. AREAS COVERED: This review summarizes the emerging data on histamine production by gut microbiota, and the effect of bacterial-derived histamine in different clinical contexts, including cancer, irritable bowel syndrome, and other gastrointestinal and extraintestinal pathologies. This review will also outline the impact of histamine on the immune system and the effect of probiotics that can secrete histamine. Search methodology: we searched the literature on PubMed up to February 2023. EXPERT OPINION: The potential of modulating gut microbiota to influence histamine production is a promising area of research, and although our knowledge of histamine-secreting bacteria is still limited, recent advances are exploring their diagnostic and therapeutical potential. Diet, probiotics, and pharmacological treatments directed to the modulation of histamine-secreting bacteria may in the future potentially be employed in the prevention and management of several gastrointestinal and extraintestinal disorders.

Histamine H1- and H4-receptor expression in human colon-derived cell lines.

In previous studies, we demonstrated the involvement of H4R in inflammatory bowel disease (IBD) and IBD-associated colon cancer in mice and could ascribe H4R-mediated histamine function to colon epithelial cells. The transferability of obtained data to humans is however lacking. Functional expression of H4R on colon epithelial cells is a prerequisite to pursue the hypothesis of involvement of H4R in carcinogenesis. Thus, we here compared the expression of histamine receptor subtypes in a series of cell lines. Out of these, three colon-derived cell lines displaying different combinations of H1R and H4R expression were submitted to functional analyses. Human hematopoietic HMC-1, HL-60, and U937, lung-derived A549 and Calu-3, and colorectal LoVo, SW 480, Caco-2, HT-29, and HCT116 cells were included in the study. mRNA expression was quantified by RT-qPCR. For functional analyses, Caco-2, HT-29, and HCT116 cells were treated by incubation with 1 - 10 µM histamine in the presence or absence of selective histamine receptor antagonists. Calcium mobilization, cAMP accumulation, and cell proliferation were measured by fluorimetry, mass spectrometry, and real-time bioimpedance measurements, respectively. Histamine receptor expression was heterogeneous in the cell lines tested. In most cell lines, we detected H1R mRNA while H4R mRNAs were found only occasionally. The colon-derived epithelial cell lines LoVo, SW480, and HT-29 expressed H1R mRNA exclusively, while in HCT116 cells H1R and H4R mRNAs and in CaCo-2 H2R mRNA were detectable. Subsequent functional analyses in HT29, Caco-2, and HCT116 cells, however, indicated that only HT-29 responded to histamine stimulation, by means of H1R. For a detailed analysis of histamine receptor function, esp. that of H1R and H4R, in human colon-derived cell lines, the cell lines tested here are not fully convenient unless genetically modified.

The Carotid Body "Tripartite Synapse": Role of Gliotransmission.

In mammals, cardiorespiratory reflexes originating in the carotid body (CB) help maintain homeostasis by matching oxygen supply to oxygen demand. CB output to the brainstem is shaped by synaptic interactions at a "tripartite synapse" consisting of chemosensory (type I) cells, abutting glial-like (type II) cells, and sensory (petrosal) nerve terminals. Type I cells are stimulated by several blood-borne metabolic stimuli, including the novel chemoexcitant lactate. During chemotransduction, type I cells depolarize and release a multitude of excitatory and inhibitory neurotransmitters/neuromodulators including ATP, dopamine (DA), histamine, and angiotensin II (ANG II). However, there is a growing appreciation that the type II cells may not be silent partners. Thus, similar to astrocytes at "tripartite synapses" in the CNS, type II cells may contribute to the afferent output by releasing "gliotransmitters" such as ATP. Here, we first consider whether type II cells can also sense lactate. Next, we review and update the evidence supporting the roles of ATP, DA, histamine, and ANG II in cross talk among the three main CB cellular elements. Importantly, we consider how conventional excitatory and inhibitory pathways, together with gliotransmission, help to coordinate activity within this network and thereby modulate afferent firing frequency during chemotransduction.

Histamine deficiency inhibits lymphocyte infiltration in the submandibular gland of aged mice via increased anti-aging factor Klotho.

OBJECTIVES: Histidine decarboxylase (HDC), a histamine synthase, is expressed in various tissues and is induced by proinflammatory cytokines such as TNFα. As they age, C57BL/6 mice show auto-antibody deposition and lymphocyte infiltration into various tissues, including salivary glands. However, the mechanism underlying cell infiltration and the change in HDC expression in salivary glands with aging remain unclear. Thus, we aimed to elucidate the relationship between histamine and inflammaging. METHODS: We investigated the change in histology and HDC expression in the major salivary glands (parotid, submandibular, and sublingual) of 6-week- and 9-month-old wild-type mice. We also determined the histological changes, cytokine expression, and anti-aging factor Klotho in the salivary glands of 9-month-old wild-type and HDC-deficient (HDC-KO) mice. RESULTS: Cell infiltration was observed in the submandibular gland of 9-month-old wild-type mice. Although most cells infiltrating the submandibular glands were CD3-positive and B220-positive lymphocytes, CD11c-positive and F4/80-positive monocyte lineages were also detected. HDC, TNFα, and IL-1ß mRNA expression increased in the submandibular gland of 9-month-old wild-type mice. The expression of PPARγ, an anti-inflammatory protein, declined in 9-month-old wild-type mice, and Klotho expression increased in 9-month-old HDC-KO mice. Immunohistochemistry showed that Klotho-positive cells disappeared in the submandibular gland of 9-month-old wild-type mice, while Klotho was detected in all salivary glands in HDC-KO mice of the same age. CONCLUSION: Our findings demonstrate the multifunctionality of histamine and can aid in the development of novel therapeutic methods for inflammatory diseases such as Sjogren's syndrome and age-related dysfunctions.

Discovery of novel benzimidazole derivatives as potent potassium-competitive acid blockers for the treatment of acid-related diseases.

H+, K+-ATPase, as the most critical enzyme in gastric acid secretion, has long been an attractive target for the treatment of acid-related diseases. In this study, a series of benzimidazole derivatives were designed and synthesized through conformational restriction and skeleton hopping strategies by using vonoprazan as the lead compound. Among them, compounds A12 (IC50 = 9.32 µM) and A18 (IC50 = 5.83 µM) showed better inhibition at the enzyme level. In addition, gastric acid secretion inhibition was assessed in vivo, and the results showed that A12 and A18 significantly inhibited basal gastric acid secretion, 2-deoxy-d-glucose (2DG) stimulated gastric acid secretion and histamine-stimulated gastric acid secretion. In further in vitro metabolic experiments, A12 and A18 demonstrated excellent stability and low toxicity. Pharmacokinetic studies showed that the p.o. and i.v. half-lives of A18 were 3.21 h and 8.67 ± 1.15 h, respectively. In summary, A18 might be a novel and effective potassium-competitive acid blocker, and this study provides strong support for it use in the treatment of acid-related diseases.

Differential regulation of histamine H1 receptor-mediated ERK phosphorylation by Gq proteins and arrestins.

Gq protein-coupled histamine H1 receptors play crucial roles in allergic and inflammatory reactions, in which the phosphorylation of extracellular signal-regulated kinase (ERK) appears to mediate the production of inflammatory cytokines. ERK phosphorylation is regulated by G protein- and arrestin-mediated signal transduction pathways. Here, we aimed to explore how H1 receptor-mediated processes of ERK phosphorylation might be differentially regulated by Gq proteins and arrestins. For this purpose, we evaluated the regulatory mechanism(s) of H1 receptor-mediated ERK phosphorylation in Chinese hamster ovary cells expressing Gq protein- and arrestin-biased mutants of human H1 receptors, S487TR and S487A, in which the Ser487 residue in the C-terminal was truncated and mutated to alanine, respectively. Immunoblotting analysis indicated that histamine-induced ERK phosphorylation was prompt and transient in cells expressing Gq protein-biased S487TR, whereas it was slow and sustained in cells expressing arrestin-biased S487A. Inhibitors of Gq proteins (YM-254890) and protein kinase C (PKC) (GF109203X), and an intracellular Ca2+ chelator (BAPTA-AM) suppressed histamine-induced ERK phosphorylation in cells expressing S487TR, but not those expressing S487A. Conversely, inhibitors of G protein-coupled receptor kinases (GRK2/3) (cmpd101), ß-arrestin2 (ß-arrestin2 siRNA), clathrin (hypertonic sucrose), Raf (LY3009120), and MEK (U0126) suppressed histamine-induced ERK phosphorylation in cells expressing S487A, but not those expressing S487TR. These results suggest that H1 receptor-mediated ERK phosphorylation might be differentially regulated by the Gq protein/Ca2+/PKC and GRK/arrestin/clathrin/Raf/MEK pathways to potentially determine the early and late phases of histamine-induced allergic and inflammatory responses, respectively.

P19-derived neuronal cells express H1, H2, and H3 histamine receptors: a biopharmaceutical approach to evaluate antihistamine agents.

Histamine is a biogenic amine implicated in various biological and pathological processes. Convenient cellular models are needed to screen and develop new antihistamine agents. This report aimed to characterize the response of neurons differentiated from mouse P19 embryonal carcinoma cells to histamine treatment, and to investigate the modulation of this response by antihistamine drugs, vegetal diamine oxidase, and catalase. The exposure of P19 neurons to histamine reduced cell viability to 65% maximally. This effect involves specific histamine receptors, since it was prevented by treatment with desloratadine and cimetidine, respectively, H1 and H2 antagonists, but not by the H3 antagonist ciproxifan. RT-PCR analysis showed that P19 neurons express H1 and H2 receptors, and the H3 receptor, although it seemed not involved in the histamine effect on these cells. The H4 receptor was not expressed. H1 and H2 antagonists as well as vegetal diamine oxidase diminished the intracellular Ca2+ mobilization triggered by histamine. The treatment with vegetal diamine oxidase or catalase protected against mortality and a significant reduction of H2O2 level, generated from the cells under the histamine action, was found upon treatments with desloratadine, cimetidine, vegetal diamine oxidase, or catalase. Overall, the results indicate the expression of functional histamine receptors and open the possibility of using P19 neurons as model system to study the roles of histamine and related drugs in neuronal pathogenesis. This model is less expensive to operate and can be easily implemented by current laboratories of analysis and by Contract Research Organizations.

GABAergic neurons in the ventral lateral geniculate nucleus and intergeniculate leaflet are involved in itch processing in mice.

Itch and pain are two closely related sensations that receiving similar encodings at multiple levels. Accumulated evidences suggest that activation of the ventral lateral geniculate nucleus and intergeniculate leaflet (vLGN/IGL)-to-lateral and ventrolateral periaqueductal gray (l/vlPAG) projections mediates the antinociceptive effects of bright light therapy. Clinical study showed that bright light therapy may ameliorate cholestasis-induced pruritus. However, the underlying mechanism and whether this circuit participates in itch modulation remains unclear. In this study, chloroquine and histamine were utilized to induce acute itch models in mice. Neuronal activities in vLGN/IGL nucleus were evaluated with c-fos immunostaining as well as fiber photometry. Optogenetic manipulations were performed to activate or inhibit GABAergic neurons in the vLGN/IGL nucleus. Our results showed that the expressions of c-fos in vLGN/IGL were significantly increased upon both chloroquine- and histamine-induced acute itch stimuli. GABAergic neurons in vLGN/IGL were activated during histamine and chloroquine-induced scratching. Optogenetic activation of the vLGN/IGL GABAergic neurons exerts antipruritic effect, while inhibiting these neurons exerts pruritic effect. Our results provide evidence that GABAergic neurons in vLGN/IGL nucleus might play a crucial role in modulating itch, which may provide clue for application of bright light as an antipruritic treatment in clinic.